insuppressible

adj

1. That cannot be suppressed.

   “It seemed as if the sense of public resentment had long been gathering strength unperceived, and now burst forth into insuppressible violence.”

   “In its stead Victor favoured Karslake with a slow smile of understanding that broadened into an insuppressible grin of successful malice, a grimace of crude exultation through which peered out the impish savage mutinously imprisoned within a flimsy husk of modern manner.”